The sludge produced by sewage treatment has high water content, and due to the feature of combination of water and the sludge particle, it is restrictive to remove the sludge by mechanical method. During the process of sewage treatment, bacteria and most parasites are found in the sludge and are accumulated as the sediment of the particles. If this kind of sludge is put into use or is discarded, it may lead to pollution to the food chain. Moreover, if not to limit the use of the sludge containing heavy metal, it would cause irreversible cultivated land degradation. The main ingredients of the sludge contain organic matters and mineral substances, so they can be used for soil improvement and as lower calorific value fuel, and after treatment, they can also be used as building materials.
At present, most sludge is discarded or landfilled, however, the resource for stacking, discarding and backfilling are becoming more and more limited. A small amount of the sludge can be dried and the made into chemical fertilizer, and agricultural use is the best method for final disposal of the sludge. In the existing technology, no one is found to be able to effectively solve the problem of high water content of the sludge during treatment, therefore, it is necessary to provide a device to dry the sludge and make them a valuable resource.